TPMS letters are displayed on my 2008 Honda Civic?

I just got a used 2008 Honda Civic & I want to know why these lights are on. When I first bought the car, it would display a little yellow round circle with an exclamation mark in the middle, which with I've been told, it means my tire had low pressure. But then a day later, that little circle light turned off & now it's displaying TPMS which means "Tire Pressure Monitoring System." I want to know what is going on? Why was there a change in lights? If the first yellow circle meant that my tire had low tire pressure, what does it mean when the TPMS yellow letters turn on?

Your vehicle tire pressure may just need to be adjusted when cold (In the morning). It could be time for the TPMS sensors replacement (5 years or older).

The light changing because from a "warning" stage now it has became a "Hard code" or defect has been detected. A TPMS scanner is in need to read out for defect code(s) store in the TPMS controller. Normally as I've seen, the code will indicate for failed TPMS sensor due to defected battery in each sensor.

The corrected repair procedure is to replace all sensors and reprogram the TPMS controller for the new sensors. HTH

Read this article:
http://www.motor.com/article.asp?article_ID=2062